Maternal vaccination against RSV: A new method to protect newborns
Every year in France, nearly 30% of infants under two years old are affected by bronchiolitis, caused by the respiratory syncytial virus (RSV) in almost three-quarters of cases. Although bronchiolitis is usually mild with spontaneous recovery in 5 to 10 days, it can sometimes take severe forms. The winter epidemic, usually from mid-November to late January, is a source of concern for parents and represents a significant burden for pediatric care systems, healthcare professionals in town, and hospitals. Currently, immunization with the monoclonal antibody Beyfortus is recommended for newborns and infants exposed to RSV for the first time. Additionally, in some cases, the treatment Synagis may also be indicated.
In August of last year, the vaccine Abrysvo received European market authorization. It is indicated for protection against lower respiratory tract diseases caused by RSV in infants from birth to 6 months of age following maternal immunization during pregnancy. The Ministry of Health has asked the HAS to evaluate the relevance of integrating this new vaccine into the RSV infection prevention strategy.
To develop its recommendation to the ministry, the HAS has considered data on immunogenicity, efficacy, safety, and acceptability of the Abrysvo vaccine. A public consultation also took place in the spring of 2024.
The HAS acknowledges the importance of vaccination to prevent RSV infections in the 8th month of pregnancy.
Regarding efficacy, estimates from the MATISSE study show a significant reduction in severe respiratory infections related to RSV: 81.8% at 3 months, 69.4% at 6 months. A reduction in hospitalizations is also observed: 67.7% at 3 months, 56.8% at 6 months. As for the vaccine’s safety, no increase in serious adverse events has been reported in either the mother or the newborn.
These data validate the importance of vaccination and lead the HAS to integrate it into the RSV infection prevention strategy for infants. However, the HAS emphasizes the importance of implementing enhanced pharmacovigilance to document a possible increased risk of preterm births (not significant for this vaccine but led to the discontinuation of the development of a competing vaccine). Pending this data, the HAS positions this vaccination as a precaution in the 8th month of pregnancy, specifically between the 32nd and 36th weeks of gestation.
Beyfortus, Abrysvo, which to choose? Informing parents for an informed decision
The HAS specifies that maternal vaccination and infant immunization with monoclonal antibodies are two alternative strategies. To present and explain them to future parents concerned, professionals are provided with a summary table of the respective advantages and disadvantages of these two strategies based on available studies.
In three situations, passive immunization with Beyfortus is preferred based on current data:
– When vaccination is unlikely to be effective (premature newborns, an interval of less than 14 days between vaccination and birth)
– In the case of a new pregnancy in a previously vaccinated mother, due to the lack of safety and effectiveness data on an additional vaccine dose
– For immunocompromised women, in the absence of efficacy and immunogenicity data of the vaccine in this population.
To allow parents to make an informed decision about the choice that suits them best, the HAS is preparing an information document that will be made available at the start of the campaign.
The practical conditions for effective prevention of RSV infections
Considering the seasonal nature of RSV, the fact that vaccines provide protection for the first six months after birth, and to facilitate family choice and adherence, the HAS recommends the simultaneous implementation of the vaccination campaign for mothers by Abrysvo and the immunization campaign for newborns and infants by Beyfortus. This corresponds to the period from September to January in metropolitan France. It is recommended to make both medications (vaccine and monoclonal antibodies) available in maternity wards to optimize the mobilization and acceptance of healthcare professionals and parents.
Vaccination of pregnant women is recommended for other diseases. The HAS specifies that the Abrysvo vaccine can be administered concurrently with a flu vaccine. However, in line with the RSV vaccine’s marketing authorization, a minimum interval of two weeks before a diphtheria-tetanus-pertussis vaccine is recommended.
Overall, the HAS emphasizes that implementing barrier measures is a complementary protective measure to maternal vaccination and infant immunization with monoclonal antibodies against RSV.
Finally, this opinion may be reviewed in light of the complete results of ongoing trials, upcoming trials, pharmacovigilance data, and real-world data from other countries.
